I think NDT is a good science communicator, he just lacks the personable quality that laypeople generally prefer when having something explained to them. Personally, I like NDT. He’s knowledgeable in his field, and when he really gets into talking about stuff you can tell he has a sense of awe and wonder about the universe. But, I think he also suffers a bit from that issue of really intelligent people just not grasping that there’s a lot of their niche knowledge that is not common knowledge. It’s not at all uncommon for NDT to put off a, “You really didn’t already know that?” vibe. I don’t at all think it’s malicious, it’s just when you reach a certain level of knowledge on a topic, it’s easy to forget how much you yourself had to learn.

TL;DR: NDT is a great science communicator if you already know enough of the basics to follow what he’s saying. Carl Sagan was an even greater communicator because he could break down subjects to explain them to people whether they were a 5 year old with a budding interest in astronomy, or a college grad studying more advanced topics.